Cup lidding apparatus and leakproof cup

Abstract

Apparatus is provided for automatically applying and heat-sealing a lid of thermoplastic film to the top of a cup. The film is supplied in a roll and the leading end is fed into a position between the top of the cup and a heat-sealing head. When the apparatus is run through an operating cycle, the cup and the head are brought together to seal a section of film to the rim of the cup and sever the section from the roll. The head is characterized by an annular heated cushion and a slitting device to from a slit in the center of the lid which enhances the seal, particularly if the cup contains a hot liquid. In an alternative arrangement, the slitting mechanism is located along the path of the film and the center of the head is constructed to prevent exposing the center of the lid to high temperature. A leakproof cup is provided in which a disposable cup is closed by a heat-sealed section of film that is relatively tight in the vicinity of the rim and relatively slack in the center in which a short, straight slit is formed.

Having thus described the invention, what we claim and desire to obtain by Letters Patent of the United States is: 
     
       1. In a cup lidding apparatus having a fixed housing adapted to contain a feed roll of heat sealable film, film advance means for drawing the leading end of said film from said roll into a heat sealing horizontally extended position above a cup, cup holding means mounted below the extended film and adapted to raise said cup up into contact with the lower face of said film and then lower said cup and a heat-sealing head mounted to said housing above the extended film and opposite said cup holder and adapted to reciprocate down against the upper surface of said film to heat seal the extended film against the rim of said cup, the improvement, comprising (a) an annular heat sealing head formed with a central opening extending entirely through said head and presenting a flat lower annular face adapted to engage the upper surface of said film and seal the lower surface against the rim of said cup while isolating the center portion of said film from the heat of said head, and,   (b) said head including resilient material therein,   (c) said head including a thermally insulating member mounted in the center of said head and extending downwardly from the lower face of said head to thermally insulate the center portion of said film from said annular face.   
     
     
       2. Apparatus according to claim 1 including film slitting means operatively associated with said apparatus for producing a relatively short straight slit in the medial portion of said film lid. 
     
     
       3. Apparatus according to claim 2 wherein said film slitting means includes a knife mounted in the center portion of the annular heat-sealing head in position to slit said film upon each heat-sealing cycle of said head. 
     
     
       4. Apparatus according to claim 2 wherein said film slitting means includes a knife mounted adjacent the path of travel of said film and reciprocating means operatively connected thereto for forming spaced slits in said film.